1. Technical Field
The present invention relates to a vertical cavity surface emitting laser and an atomic oscillator.
2. Related Art
A vertical cavity surface emitting laser (VCSEL) is, for example, used as a light source of an atomic oscillator using coherent population trapping (CPT) which is a type of quantum interference effects.
In the vertical cavity surface emitting laser, a resonator generally has an isotropic structure, and accordingly it is difficult to control a polarization direction of the laser light emitted from the resonator. JP-A-11-54838, for example, discloses a vertical cavity surface emitting laser which generates distortion in a resonator by a distortion imparting portion and causes double refraction to occur, so as to stabilize a polarization direction of laser light.
However, in the vertical cavity surface emitting laser disclosed in JP-A-11-54838, a magnitude of the distortion generated in the resonator by the distortion imparting portion is not sufficient, and thus the polarization direction of the laser light may not be stabilized.